html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
	margin: 0;
	padding: 0;
	border: 0;
	font-size: 100%;
	font: inherit;
	/* vertical-align: baseline; */
  /* color: #222; */
  font-family: Helvetica, Tahoma, Arial, STXihei, "华文细黑", "Microsoft YaHei", "微软雅黑", SimSun, "宋体", Heiti, "黑体", sans-serif;
}

.usercenter{
    width: 100%;
    position:fixed;
    top:0;
    bottom: 0;
    background: #222;
    z-index:100
}
.back{
    position: absolute;
    top:0;
    left:5px;
    z-index:50;
}
.icon-back{
    position: absolute;
    top:10px;
    left:15px;
    z-index:50; 
    width:30px;
    height:30px;
}